Answer:
Distributive property
Explanation:
The given equation is:
![2q(q+4)=10](https://img.qammunity.org/2020/formulas/mathematics/high-school/qfm0eb2mdj8zkc2acmmen6vgnv639ozmmt.png)
To solve this equation, we expand the left hand side using the distributive property to obtain:
![2q^2+8q=10](https://img.qammunity.org/2020/formulas/mathematics/high-school/xm9a7ryrmwxoalpskle6ehapj7o6jehny4.png)
That was exactly what Miskai did.
Therefore the property that justifies his step shown is the distributive property.
This property says that, if a, b, and c are real numbers then,
![a(b+c)=ab+bc](https://img.qammunity.org/2020/formulas/mathematics/high-school/733dqsxc8jm6agf0atf9iigrxod461jr3f.png)